This invention relates generally to oil testing methods and apparatus, and more particularly to a method and apparatus for testing the lubricating condition of engine oils.
Synthetic lubricating oils used in internal combustion engines, such as, for example, aircraft engines, contain engine additives which are blended in the oil to enable it to withstand higher temperatures, etc., before oxidation and acid build-up occurs. Also added to the oil is what is known as an inhibitor. Its purpose is to consume oxidation by-products as they are formed in the oil in an attempt to prolong the life of the oil.
Even with the above described additives and inhibitors, oil eventually breaks down and is no longer a satisfactory lubricant. The inhibitors eventually lose their ability to consume any additional oxidation by-products and become depleted. When this occurs, an engine in which the oil is used may be damaged, partially or completely so as to require a complete overhaul. This can be costly both monetarily and, in the case of aircraft engine breakdown, in human life.
Several oil testing techniques are now in use to periodically determine the lubricating state or condition of oil being used in aircraft or the like engines. These tests are: The titration test which measures the acid content of oil samples (acid build-up thought of as being indicative of an unsatisfactory oil); spectroanalysis, wherein the percentages of oxides and acids formed in the oil are determined; and electrical conductivity wherein the ability of the oil to be electrically conductive is determined (the resistivity of the oil indicating the degradation thereof).
All of the methods require that a sample of the oil taken from the engine be transported to a laboratory to be tested by equipment located thereat. This procedure normally takes about three full days before a report can be obtained. In most instances, especially in the case of aircraft, an airline cannot wait the full three days and schedules the aircraft back into service without receiving the test data. This often results in damaged aircraft engines, or even a disastrous plane crash.